Running test suite with refleak hunter reports test_asyncio leaks referrences:

0:00:00 [1/1] test_asyncio
Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.123 seconds
beginning 9 repetitions
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Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.112 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.104 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.113 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.104 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.120 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.142 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.141 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.107 seconds
.Executing <Task finished coro=<CoroutineTests.test_async_def_wrapped.<locals>.start() done, defined at /home/angwer/repos/cpython/Lib/test/test_asyncio/test_pep492.py:150> result=None created at /home/angwer/repos/cpython/Lib/asyncio/base_events.py:445> took 0.115 seconds
.
test_asyncio leaked [-2, 2, 0, 0] memory blocks, sum=0
test_asyncio failed in 4 min 27 sec

1 test failed:
    test_asyncio

git bisect blames ba7e1f9a4e06c0b4ad594fd64edcaf7292515820. Looking at the patch it looks to me the problem is in test_get_event_loop_new_process(), the pool is not shutdown.